Measuring Seven Platinum RTD Temperatures with One Reference Resistor and One Reference Current

The LTC2428 is a 8-channel 2.7V to 5.5V micropower 20-bit A/D converters with an integrated oscillator, 8ppm INL and 1.2ppm RMS noise. It uses a delta-sigma technology and provide single cycle digital filter settling time (no latency delay) for multiplexed applications. The first conversion after the channel is changed is always valid. Through a single pin the LTC2428 can be configured for better than 110dB rejection at 50Hz or 60Hz ±2%, or can be driven by an external oscillator for a user defined rejection frequency in the range 1Hz to 800Hz. The internal oscillator requires no external frequency setting components.